1. Field of the Invention
The present invention relates to an indication display unit for displaying velocity, revolution number or the like in vehicles, and more particularly to a display unit equipped with a head-up projector for displaying an image projected to a semi-translucent mirror, a windshield or the like located in front of a driver seat.
2. Description of the Prior Art
Various indication display units for vehicles provided with such a head-up display (hereinafter refer to "HUD") have been suggested by now. The most widely used HUD type indication display unit comprises a display device such as LCD cell, a light source and an optical system for image projection, and a projecting surface composed of a windshield or a semi-translucent mirror located in front of it so as to project an image to the projecting surface. However, since the projecting surface of such HUD is flat, when the driver's eyes are averted from the front forward direction of the car, for example when the car is turning round a curve, or generally when the position of the eye level is inclined too much towards right or left due to the difference of the driving style of each driver, there are occasions in which the displayed image can be hardly seen on the projecting surface. Specially when a lens is used to put the indicating image farther ahead, the visible range of the indicating image becomes much narrower.
Problems to be Solved.
It is an object of the present invention to eliminate the foregoing difficulties in the conventional display unit, and to provide an HUD type display unit for vehicles, which is capable of having the driver view the indicating image at any eye level.
Means to solve the problem
In order to attain the above object the present invention provides an indication display unit characterized in that the projecting surface has a concave curvature whose center of curvature 0 is positioned in a point made by a bisector of PQP' intersecting the line PP' wherein P stands for the mounting position of a projector device, Q a reflecting point on a projecting surface, and P' the position of driver's eye in the normal seating position.
Advantage of the Invention
As shown above, the present invention is provided with a concave surface, on which an indicating image is projected, having a preset point as its center of curvature.
Thus, even when the driver's eyes are shifted away from the front forward direction of the vehicle, as the distance between his eyes and the projecting surface remains the same; the driver can still sight the indicating image and can consequently obtain a much wider visual field of the projected indicating image.